Pluripotent stem cells are undifferentiated cells that have the capacity to differentiate into the various cell types that form an organism (pluripotency). Pluripotent stem cells also have the capacity to undergo self-renewal (self-renewal capacity) in a state in which pluripotency is maintained (typically an undifferentiated state) and as a consequence can be cultured (maintained) on a long-term basis in a state in which pluripotency is maintained (typically an undifferentiated state). In view of this pluripotency and self-repair capacity (proliferative capacity), there are high expectations for pluripotent stem cells as a cell resource for use in regenerative medicine, for example, cell transplantation therapy. These pluripotent stem cells can be specifically exemplified by induced pluripotent stem cells (also referred to as “iPS cells” hereinafter), embryonic stem cells (also referred to as “ES cells” hereinafter), and muse cells (multi-lineage differentiating stress enduring cell).
In particular, iPS cells are cells that have acquired pluripotency and self-renewability through an artificial reprogramming of differentiated cells (typically somatic cells, for example, dermal fibroblasts). That is, iPS cells can be produced using a patient's own somatic cells (differentiated cells). Due to this, rejection reactions and ethical problems either do not occur with iPS cells or are minor, and as a consequence iPS cells are expected to be cells that have advantages as a cell resource for regenerative medicine and research into their clinical applications has been rapidly advancing.